1. Field of the Invention
The present invention relates to an ion source.
2. Related Background Art
As disclosed in Japanese Patent Laid-open No. 2004-39459, an ion source is known in which ions are extracted from plasma generated within a discharge chamber to emit an ion beam. Such an ion source is for example used in an ion beam etching apparatus (also called an ion milling apparatus). When used in an ion beam etching apparatus, by irradiating the surface of a substrate with the ion beam emitted from the ion source, the substrate can be etched.